金属离子修饰的铂纳米金属簇催化2,3-戊二酮区域选择性氢化

近年来,α-二酮的不对称氢化引起了人们的极大兴趣1～3].由于α-二酮分子内存在两个共轭的羰基,α-二酮的氢化包括两步反应,通过控制反应条件可以使反应停留在第一步氢化的阶段3].在已往的文献报道中1～3],氢化反应的底物均局限于对称的α-二酮,如2,3-丁二酮或3,4-己二酮.这类底物的第一步氢化并不涉及区域选择性的问题.以2,3-丁二酮为例,第一步氢化只生成3-羟基-2-丁酮一种产物.但是,象2,3-戊二酮之类的不对称α-二酮的氢化情况则复杂得多,因为在第一步反应中有2-羟基-3-戊酮和3-羟基-2-戊酮两种产物生成.因此,在研究不对称α-二酮的对映体选择性氢化时还必须顾及其区域选择性氢化.

Regioselective Hydrogenation of 2,3-Pentanedione over Modified Platinum Nanoclusters

Regioselective hydrogenation of 2,3 pentanedione was investigated over poly ( N vinyl 2 pyrrolidone) stabilized platinum nanoclusters (PVP Pt) with metal cation as modifier. The results indicated that the addition of metal cations as well as the increase of solvent polarity could enhance the regioselectivity for 3 hydroxy 2 pentanone. The use of Sn 2+ could remarkably activate the hydrogenation reaction while the use of Ce 3+ decreased the reaction activity greatly. The modification effect was explained by the toxic effect of metal cations on the metal catalyst, the polarization effect of metal cations on the carbonyl group and the steric effect of the substrate itself.